Typical procedures for treating chronic wounds such as, for example, venous ulcers, diabetic ulcers and pressure sores, include the use of absorbent dressings or hydrocolloid gels. Additionally, since most chronic wounds are infected, many wound dressings contain antimicrobial agents, such as silver or iodine, to either create a barrier to microorganisms or reduce microbial load. These treatments are used more for managing the wound environment and moisture balance than actively promoting wound healing.
Inflammation and the timely release of reactive oxygen species (ROS) are critical for normal wound repair and, together with proteolytic and other cytotoxic enzymes, serve to kill ingested bacteria and prevent wound infection. However, due to other circumstances such as patient nutrition, co-morbidities (smoking, diabetes), or poor blood circulation due to patient positioning, the inflammatory phase may last too long resulting in the creation of excess ROS that actually damage surrounding tissue including healthy tissue forming within the wound. Excess ROS, also known as “free radicals,” can be detrimental to tissue because they also damage cells and extracellular matrix components such as collagen. Additionally, ROS can act as signaling molecules to recruit matrix metallo proteases (MMPs) and other proteases to the wound site. Normal endogenous levels of MMPs are essential for tissue remodeling during the wound healing process. However, in excess, they continually break down the new tissue that is formed. This leads to a wound that either does not heal quickly or becomes “stalled.” Excess levels of ROS and MMPs create a sustained state of inflammation thereby preventing the progression of normal wound healing.
Elevated levels of MMPs have been remedied by preventing activation of MMPs or by use of MMP inhibitors. Some wound dressings on the market use various forms of natural collagen as a sacrificial substrate for MMPs because the collagen also provides the mechanical properties (integrity) necessary to form the dressing. Topical application of antioxidants to a wound may reduce ROS levels, subsequently helping a chronic wound to re-enter a normal healing state.